IMPACT OF URBAN VEGETATION ON SOLAR IRRADIANCE: A COMPARATIVE STUDY IN THE CITY OF ZAGREB

Urban areas are characterized by very intense and complex interactions between built objects and natural elements, especially in terms of the impact they have on the local microclimate. One of the most important aspects of this interaction is the way in which vegetation influences incident solar radiation, which has a major impact on energy consumption, comfort and the overall sustainability of urban areas. In this study, we focus on the city of Zagreb, where we conduct a detailed analysis of the impact of urban vegetation on solar radiation, comparing areas with and without high vegetation. For this purpose, we calculated a digital surface model (DSM) from high-resolution LiDAR data. LiDAR technology enables very good mapping of both the terrain and above-ground features such as buildings and vegetation. The creation of two different DSMs - one with high vegetation and one without - allows us to isolate the specific effects of vegetation on solar radiation. The analysis was performed in WhiteboxTools using the TimeInDaylight command, which calculates the daylight in a landscape over a given period of time. This command takes into account the position of the sun and topographic features in the DSMs for accurate modeling of solar radiation. The result shows that solar radiation is different in areas with and without dense vegetation. The study found that tall vegetation, such as trees, greatly reduces solar radiation on the ground and surrounding buildings. A reduced impact of solar radiation can lead to cooler surface temperatures and a lower cooling demand in summer, contributing to higher thermal comfort in urban areas. Without vegetation, radiation would be much higher, increasing heat build-up and thus the extent of the urban heat island.